JP7450646B2 - wafer boat - Google Patents

Description

The present disclosure relates to wafer boats.

Conventionally, in the manufacturing process of semiconductor devices such as LSIs, wafers are processed at 1200°C in order to form an oxide film on the surface of a semiconductor wafer (hereinafter simply referred to as "wafer") or to diffuse dopants. It includes a process of heat treatment at a high temperature of about ℃. In such a heat treatment process, a wafer boat as described in Patent Document 1 is used to place a plurality of wafers at predetermined intervals in the horizontal direction.

Japanese Patent Application Publication No. 11-126755

A wafer boat according to the present disclosure includes a plurality of columnar supports each having a plurality of grooves for placing wafers thereon, and support plates that respectively support both ends of the supports. The pillar is made of ceramics whose main component is aluminum oxide or silicon carbide, and the outer surface of the pillar is at least one of a ground surface and a polished surface.

1 is a photograph showing a wafer boat according to an embodiment of the present disclosure. (A) is an explanatory diagram showing a strut provided in a wafer boat according to one embodiment, and (B) is an explanatory diagram when the strut shown in (A) is viewed from the direction of arrow A. It is an explanatory view showing a support plate with which a wafer boat concerning one embodiment is equipped. It is an explanatory view showing a state where a pillar is fixed to a support plate. 5 is a photograph showing a wafer boat according to another embodiment of the present disclosure. 6 is a photograph of the wafer boat shown in FIG. 5 taken from an oblique direction.

In the conventional wafer boat as described in Patent Document 1, the support rods (pillars) may undulate or warp due to the manufacturing method or the like. As a result, the conventional wafer boat cannot accurately maintain the axial straightness of the outer circumferential surface of the support rod or the perpendicularity of the outer circumferential surface with respect to the end surface of the support rod. Therefore, it is difficult to accurately form a groove for placing a wafer.

As described above, in the wafer boat according to the present disclosure, the outer surface of the support column is at least one of a ground surface and a polished surface. Therefore, the straightness of the column in the axial direction and the perpendicularity of the outer surface with respect to the end surface of the column are improved compared to the case where the column is a burnt-out surface. As a result, the perpendicularity of the virtual central planes of the grooves with respect to the outer surface and the parallelism between the virtual central planes of adjacent grooves are improved. Therefore, when the wafer boat according to the present disclosure is used, a plurality of wafers can be placed in a regularly arranged state.

A wafer boat according to an embodiment of the present disclosure will be described based on FIGS. 1 to 6. A wafer boat 1 according to an embodiment shown in FIG. 1 includes a columnar support 2 and a support plate 3. The wafer boat 1 shown in FIG. As shown in FIG. 1, the wafer boat 1 according to one embodiment is provided with a rod-shaped member 5 different from the support column 2. This rod-shaped member 5 does not have a groove 21, which is provided in the support column 2, and is used as a so-called reinforcing material.

A wafer boat 1 according to an embodiment shown in FIGS. 5 and 6 includes a prismatic support column 2 and a support plate 3. The wafer boat 1 shown in FIGS. 5 and 6 does not have the rod-shaped member 5, and the support columns 2 also function as reinforcing members, so that the weight can be reduced.

The column 2 shown in FIGS. 1 and 5 includes a plurality of grooves 21 for placing wafers. The size of the support 2 is not limited, and is appropriately designed depending on the number and size of wafers to be placed. The strut 2 has a length (total length) of approximately 120 mm or more and 180 mm or less, for example. The columnar support 2 may have a thickness (diameter) of about 8 mm or more and 12 mm or less. The prismatic pillar 2 may have a square cross-sectional shape in the direction perpendicular to the axis, and the length of one side may be approximately 4 mm or more and 12 mm or less.

The support 2 shown in FIG. 1 has only a cylindrical shape, and the support 2 shown in FIG. 5 has only a prismatic shape. However, the wafer boat 1 may include both cylindrical and prismatic columns 2.

The pillars 2 are made of ceramics whose main component is aluminum oxide or silicon carbide. The pillars 2 are not limited as long as they are made of ceramics whose main component is aluminum oxide or silicon carbide. As used herein, the term "main component" refers to a component that accounts for 80% by mass or more of the total 100% by mass of the components constituting the ceramic. Identification of each component contained in the ceramic is performed using an X-ray diffraction device using CuKα rays, and the content of each component is determined using, for example, an ICP (Inductively Coupled Plasma) emission spectrometer or a fluorescent X-ray spectrometer.

When the ceramic has aluminum oxide as a main component, it may contain magnesium, silicon, and calcium as oxides. In terms of oxides, for example, the magnesium content is 0.034 mass% or more and 0.36 mass% or less, the silicon content is 0.02 mass% or more and 0.7 mass% or less, and the calcium content is 0.02 mass% or more and 0.7 mass% or less. is from 0.011% by mass to 0.065% by mass.

The depth, width, and number of grooves 21 for placing wafers are not limited. The depth, width, and number of grooves 21 are appropriately designed depending on the number and size of wafers to be placed.

The cross-sectional shape of the groove 21 may be in the form of an isosceles trapezoid, with the opening side being wider than the mounting surface side. With such a shape, when a wafer is inserted and placed in the groove 21, the risk of the wafer coming into contact with the inner surface forming the groove 21 is reduced. The apex angle of the groove when viewed in cross section is, for example, 18° or more and 42° or less, particularly preferably 20° or more and 40° or less.

In the wafer boat 1 according to one embodiment, the outer surface of the support column 2 is at least one of a ground surface and a polished surface. When the outer surface of the column 2 has a surface processed in this way, the straightness of the outer surface in the axial direction and the perpendicularity of the outer surface with respect to the end surface of the column 2 are affected by the baked surface (unground surface). and unpolished surfaces). Therefore, the perpendicularity of the virtual center planes of the grooves 21 with respect to the outer circumferential surface and the parallelism between the virtual center planes of adjacent grooves 21 are improved. As a result, a plurality of wafers can be regularly aligned.

Grinding or polishing is performed, for example, by surface grinding, centerless grinding, brush polishing, buff polishing, or the like.

In the groove 21 provided in the support column 2, the surface on which the wafer is placed may be at least one of a ground surface and a polished surface. In this case, the arithmetic mean roughness Ra of the wafer mounting surface is preferably smaller than the arithmetic mean roughness Ra of the outer surface. Since the groove 21 provided in the support column 2 has such a structure, when a wafer is placed in the groove 21, the possibility that the wafer is damaged can be reduced.

In the groove 21 provided in the support column 2, the arithmetic mean roughness Ra of the wafer mounting surface is not limited. For example, the arithmetic mean roughness Ra of the wafer mounting surface is preferably about 0.02 μm or more and 0.3 μm or less. Further, as long as the arithmetic mean roughness Ra of the wafer mounting surface is smaller than the arithmetic mean roughness Ra of the outer surface, the difference is not limited. For example, the difference between the arithmetic mean roughness Ra of the wafer mounting surface and the arithmetic mean roughness Ra of the outer surface may be 0.05 μm or more. The arithmetic mean roughness Ra of the wafer placement surface is approximately 0.02 μm or more and 0.3 μm or less, and the difference between the arithmetic mean roughness Ra of the wafer placement surface and the arithmetic mean roughness Ra of the outer surface is 0.02 μm or more and 0.3 μm or less. If the thickness is 0.05 μm or more, the possibility that the wafer will be damaged when the wafer is placed in the groove 21 can be further reduced.

The arithmetic mean roughness Ra of the mounting surface of the wafer and the arithmetic mean roughness Ra of the outer surface are both measured using a laser microscope (manufactured by Keyence Corporation, VK-X1100 or its (successor model). The measurement conditions are: first, the magnification is 480 times, there is no cut-off value λs, the cut-off value λc is 0.08 mm, there is no cut-off value λf, and each point is measured from the mounting surface and the outer surface to be measured. The measurement range of each is set to 705 μm×530 μm. Here, in setting the measurement range, it is sufficient to select a representative part showing the characteristics of the surface from among the surfaces observed at a magnification of 480 times.

Then, in the measurement range, four lines to be measured are drawn at approximately equal intervals, the surface roughness is measured, the average value of the arithmetic mean roughness Ra is determined for each surface, and the two are compared. The length of each line is 560 m, and the direction of the line may be the same as the direction of the polishing streaks and polishing streaks observed on the mounting surface and the outer surface.

Both ends of the support column 2 have plate-shaped engagement portions 22, as shown in FIG. 2(B). A through hole 23 for inserting the male screw 4 in the thickness direction is formed in the flat engagement portion 22 . That is, it is formed in a direction perpendicular to the axial direction (longitudinal direction) of the support column 2. The through hole 23 is formed coaxially with a female thread (not shown) provided on the support plate 3, and the male screw 4 is inserted into the through hole 23 and attached to the support plate 3.

The method of manufacturing the support column 2 is not limited, and for example, the support column 2 can be manufactured in the following manner. First, a case in which the pillars are formed of ceramics containing aluminum oxide as a main component will be described. Aluminum oxide powder (purity of 99.9% by mass or more), which is the main component, and each powder of magnesium hydroxide, silicon oxide, and calcium carbonate are charged into a grinding mill together with a solvent (ion-exchanged water). After pulverizing the powder until the average particle size (D50) becomes 1.5 μm or less, an organic binder and a dispersant for dispersing the aluminum oxide powder are added and mixed to obtain a slurry.

Here, the content of magnesium hydroxide powder in the total 100% by mass of the above powder is 0.05% by mass or more and 0.53% by mass or less, and the content of silicon oxide powder is 0.02% by mass or more and 0.7% by mass. Hereinafter, the content of calcium carbonate powder is 0.02% by mass or more and 0.12% by mass or less, and the remainder is aluminum oxide powder and unavoidable impurities. Examples of the organic binder include acrylic emulsion, polyvinyl alcohol, polyethylene glycol, and polyethylene oxide.

Next, the slurry is spray granulated to obtain granules whose main component is aluminum oxide. The granules are filled into a molding space in a cold isostatic pressing device and pressurized at a molding pressure of, for example, 78 MPa to 128 MPa to obtain a cylindrical or prismatic molded body. Next, after forming plate-shaped engagement parts with through holes at both ends of the molded body by cutting, etc., the firing atmosphere is atmospheric, the firing temperature is 1500°C or more and 1700°C or less, and the holding time is 4 hours or more. A columnar sintered body can be obtained by firing the molded body for 6 hours or less.

A case where the pillars are formed of ceramics containing silicon carbide as a main component will be described. Coarse granular powder and fine granular powder are prepared as silicon carbide powder, and the silicon carbide powder is charged into a pulverizing mill together with a solvent and a dispersant, and pulverized and mixed to form a slurry. The time for pulverization and mixing is 40 hours or more and 60 hours or less. After pulverization and mixing, the particle sizes of the fine granular powder and the coarse granular powder are in the range of 0.4 μm to 4 μm, and 11 μm to 34 μm.

Next, a sintering aid consisting of boron carbide powder, amorphous carbon powder or phenolic resin, and a binder are added to the resulting slurry and mixed, and then spray-dried to carbonize the main components. Granules consisting of silicon are obtained. A molded body obtained by molding the granules by the method described above is cut or the like to form plate-shaped engagement portions having through holes at both ends of the molded body. Thereafter, a degreased body is obtained in a nitrogen atmosphere at a temperature of 450° C. to 650° C. and a holding time of 2 hours to 10 hours. Next, a columnar sintered body can be obtained by firing the degreased body under a reduced pressure atmosphere of inert gas, a firing temperature of 1800°C or more and 2200°C or less, and a holding time of 3 hours or more and 6 hours or less. .

By processing the outer surface of the above-mentioned columnar sintered body by centerless grinding with a rotary grindstone, brush polishing, buff polishing, etc., a columnar support can be obtained. When the sintered body has a prismatic shape, it can be made into a prismatic support by processing the outer surface by surface grinding. The groove is formed by V-groove grinding using a rotary grindstone having an acute-angled outer peripheral tip. Brush polishing, buff polishing, etc. may be applied as necessary. In order to obtain a wafer boat in which the mounting surface has a smaller arithmetic mean roughness Ra than the outer surface, for example, if the grain size of the rotary grindstone used for forming the grooves is made finer than the grain size of the rotary grindstone used for forming the outer surface. good.

The male screw 4 is screwed into the female screw provided on the support plate 3 through a through hole 23 formed in the flat plate-shaped engagement portion 22 . Since the support column 2 is mechanically attached to the support plate 3 with screws, the wafer is less likely to become unstable during transportation. As a result, the possibility of damage to the wafer can be further reduced.

The support plate 3 is used to support (fix) both ends of the column 2. The size of the support plate 3 is appropriately designed depending on the size of the wafer to be placed, the length of the support column 2, and the like. The support plate 3 is made of ceramics, for example. Examples of ceramics include ceramics containing aluminum oxide or silicon carbide as a main component. For the purpose of weight reduction, at least one of the support plates 3 may have a hollow structure. Having a hollow structure improves the convection of the cleaning liquid when used as a cleaning component. Furthermore, since there is less residual liquid during drying, cleaning efficiency is improved.

The shape of the support plate 3 is not limited as long as it can support both ends of the support column 2. For example, as shown in FIG. 3, the peripheral edge of the support plate 3 may be formed into an uneven shape to match the shape of both ends of the support column 2. The strut 2 is arranged in this uneven portion so that both ends of the strut 2 are located as shown in FIG. 4, and is fixed, for example, with the male screw 4 as described above. The male thread 4 is also made of ceramic, for example. Examples of ceramics include ceramics containing aluminum oxide or silicon carbide as a main component.

The method for manufacturing the support plate 3 is not limited, and for example, the support plate 3 can be manufactured as follows. First, the granules obtained by the method described above are filled into a molding space in a cold isostatic pressing device. A plate-shaped molded body is obtained by applying a molding pressure of, for example, 78 MPa or more and 128 MPa or less. Next, the molded body is shaped into a precursor of the support plate 3 by cutting or the like. Thereafter, a sintered body can be obtained by appropriately selecting firing conditions depending on the main component and firing the precursor. Each surface of this sintered body may be ground or polished as necessary.

The support column 2, the support plate 3, and the male screw 4 may be made of ceramics having different main components, or may be made of ceramics having the same main component. Ceramics having the same main component do not necessarily have the same content of the main component, and the content of the main component may be different. For example, if the main component is aluminum oxide, the content of aluminum oxide may be different.

When the pillar 2, the support plate 3, and the male screw 4 are formed of ceramics having the same main component, the proportion of the main component contained in each member is not limited. For example, regarding the content of the main components, it is preferable to minimize the content of the main components of the external thread 4. For example, when cleaning the wafer boat 1 according to one embodiment, the pillars 2 and the support plate 3, which have a larger surface area than the male screw 4, have a larger area in contact with the cleaning liquid. Therefore, by increasing the content of the main components of the pillars 2 and the support plate 3 (increasing the purity), corrosion can be suppressed even when cleaning with acid or alkali. As a result, the wafer boat 1 according to one embodiment can be used for a long period of time.

The content of the main components is not limited as long as the content of the main components of the male thread 4 is minimized. For example, the difference between the main components contained in the strut 2 and the main components contained in the male thread 4 may be 0.15% by mass or more. By having such a difference, corrosion can be further suppressed and it can be used for a longer period of time.

The surfaces of the fully threaded portion of the male thread 4 and the fully threaded portion of the female thread provided on the support plate 3, as well as the inner wall surface of the through hole 23 formed in the flat plate-shaped engagement portion 22 provided at both ends of the support post 2. At least one side may be an unburned surface. Since the unbaked surface has a low contact angle with pure water and is highly hydrophilic, the wafer boat 1 according to the embodiment can be efficiently cleaned even when the male thread 4 is screwed into the female thread. In particular, it is preferable that the surfaces of the fully threaded portion of the male thread 4 and the fully threaded portion of the female thread provided on the support plate 3 be burnt-out surfaces. Since the surface of the fully threaded portion has large irregularities, the bonding force is strong and the reliability of impact resistance and vibration resistance is improved.

At least one of the strut 2, the support plate 3, and the male screw 4 may be formed of ceramics having closed pores. In this case, the value (A) obtained by subtracting the average value of the equivalent circle diameter of the closed pores from the distance between the centers of gravity of adjacent closed pores is preferably 20 μm or more and 85 μm or less. If this value (A) is 20 μm or more, the voids are not densely packed but are dispersedly arranged in the ceramic. Therefore, higher mechanical properties are exhibited. On the other hand, if the value (A) is 85 μm or less, workability such as polishing is further improved. Furthermore, when the value (A) is within such a range, the distance between adjacent closed pores becomes narrow. Therefore, the extension of microcracks caused by thermal shock or the like can be suppressed.

The value (A) can be determined by the following method. First, the pillar 2 is polished in the depth direction (longitudinal direction) from a cross section perpendicular to the longitudinal direction using a copper disc using diamond abrasive grains having an average grain size D ₅₀ of 3 μm. Thereafter, a polished surface is obtained by polishing with a tin disk using diamond abrasive grains having an average grain size D ₅₀ of 0.5 μm.

Observe the polished surface at 200x magnification, select an average range, and select a range with an area of 0.105 mm ² (horizontal length: 374 μm, vertical length: 280 μm) using the CCD. Obtain an observation image by taking a picture with a camera. Using this observed image as a target, the distance between the centers of gravity of the open pores was measured using the image analysis software "A-zo-kun (ver 2.52)" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.) using a method called the center-to-center distance method of dispersion measurement. Just find the distance. Hereinafter, when the image analysis software is referred to as "Azo-kun", it refers to the image analysis software manufactured by Asahi Kasei Engineering Co., Ltd.

Setting conditions for this method include, for example, a threshold value of 86, which is an index indicating the brightness of an image, a brightness of dark, a small figure removal area of 1 μm ² , and a noise removal filter. The threshold value may be adjusted depending on the brightness of the observed image. The brightness was set to dark, the binarization method was set to manual, the small figure removal area was set to 1 μm ² , and a noise removal filter was used, and the threshold value was set so that the marker appearing in the observed image matched the shape of the pore. Just adjust it.

The equivalent circular diameter of a closed pore can be determined by the following method. The equivalent circle diameter of the closed pores may be determined using a technique called particle analysis using the above observed image. The setting conditions for this method may be the same as those used for the center-of-gravity distance method for dispersion measurement.

In the case of the support plate 3, a polished surface may be prepared in the thickness direction of the support plate 3 using the same method as described above, and the value (A) may be determined using the same method as described above for this polished surface. In the case of the male screw 4, a polished surface is prepared in the depth direction (longitudinal direction) from a cross section perpendicular to the longitudinal direction of the male screw 4 using the same method as described above, and this polished surface is subjected to the same method as described above. All you have to do is find the value (A).

To obtain the pillar 2, support plate 3, and male screw 4 having a value (A) of 20 μm or more and 85 μm or less, when obtaining ceramics whose main component is aluminum oxide, the firing temperature should be set at 1500°C or more and 1600°C or less, and the firing atmosphere After firing the molded body in an air atmosphere for a holding time of 5 hours or more and 6 hours or less, heat treatment is performed, for example, at a heat treatment temperature of 1300° C. or more and 1600° C. or less, an argon atmosphere as the heat treatment atmosphere, and a pressure of 90 MPa or more and 300 MPa or less. Bye.

As described above, the wafer boat 1 according to one embodiment can place a plurality of wafers in a regularly aligned state. The wafer boat 1 according to this embodiment is included in a heat treatment device for heat treating wafers, a cleaning device for cleaning wafers, and the like.

The wafer boat according to the present disclosure is not limited to the above-described embodiment. For example, the wafer boat 1 according to one embodiment is equipped with four pillars 2. However, in the wafer boat according to the present disclosure, at least two columnar supports may be provided as long as they are arranged so as to be able to hold wafers.

In the wafer boat 1 according to one embodiment, the support column 2 is supported by the support plate 3 using a male screw 4. However, in the wafer boat according to the present disclosure, the means for supporting the columnar supports on the support plate is not limited, and may be supported using an adhesive, glass bonding, diffusion bonding, etc., for example.

In the wafer boat 1 according to one embodiment, the peripheral edge of the support plate 3 is formed into an uneven shape to match the shape of both ends of the support column 2. However, in the wafer boat according to the present disclosure, the shape of the support plate is not limited, and the peripheral edge of the support plate does not need to be formed in an uneven shape.

The wafer boat 1 according to one embodiment is provided with a rod-shaped member 5 different from the support column 2 as a reinforcing member. However, in the wafer boat according to the present disclosure, such a rod-shaped member is a member that is optionally used, and is not necessarily a member that must be used.

1 Wafer boat 2 Support 21 Groove 22 Flat engagement portion 23 Through hole 3 Support plate 4 Male thread 5 Rod-shaped member

Claims (11)

comprising a plurality of columnar supports each having a plurality of grooves for placing wafers thereon, and support plates each supporting both ends of the supports,
The pillar is made of ceramics containing aluminum oxide or silicon carbide as a main component, and the outer surface of the pillar is at least one of a ground surface and a polished surface,
Both ends of the support are provided with flat plate-like engagement parts having through holes in the thickness direction,
Each of the support plates is provided with a female thread on the axis of the through hole,
a male thread is screwed into the female thread through the through hole;
wafer boat. The mounting surface on which the wafer is mounted in the groove is at least one of a ground surface and a polished surface, and the mounting surface has an arithmetic mean roughness Ra smaller than the outer surface. wafer boat. 3. The wafer boat according to claim 2 , wherein the groove has an isosceles trapezoidal cross-sectional shape that is wider on the opening side than on the placement surface side. The wafer boat according to any one of claims 1 to 3, wherein the support column, the support plate, and the male screw are formed of ceramics having the same main component, and the male screw has the smallest content of the main component. The wafer boat according to claim 4 , wherein the content of the main component contained in the strut is at least 0.15% by mass greater than the content of the main component contained in the male thread. The wafer boat according to claim 4 or 5 , wherein at least one of the surfaces of the fully threaded portion of the female thread and the fully threaded portion of the male thread, and the inner wall surface of the through hole are baked surfaces. The wafer boat according to any one of claims 1 to 6 , wherein the through hole is an elongated hole extending in the axial direction of the support column. At least one of the support column, the support plate, and the male screw is formed of ceramics having closed pores, and a value obtained by subtracting the average value of the equivalent circle diameter of the closed pores from the distance between the centers of gravity of the adjacent closed pores. The wafer boat according to any one of claims 1 to 7 , wherein (A) is 20 μm or more and 85 μm or less. The wafer boat according to claim 1, wherein at least one of the support plates has a hollow structure. A heat treatment apparatus comprising the wafer boat according to any one of claims 1 to 9 . A cleaning device comprising the wafer boat according to any one of claims 1 to 9 .

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